A light detection apparatus includes one or more light detection devices and an integrating circuit for outputting a voltage having a value consonant with the amount of electrical charges output by the light detection devices. In this light detection apparatus, electrical charges output by the light detection devices, in amounts equivalent to the intensity of the incident light, are integrated in the integrating circuit and are output by the integrating circuit as a voltage having a value consonant with the amount of the integrated charges, and based on this voltage, the intensity of the incident light is obtained.
The light detection apparatus may further include an A/D converter circuit for converting into a digital signal a voltage (analog signal) output by the integrating circuit. In this case, the intensity of the incident light can be obtained as a digital value, and can be processed by a computer and the like. When multiple light detection devices are arranged, either one-dimensionally or two-dimensionally, the light detection apparatus can be employed as a solid-state image pickup apparatus.
The CMOS technique can be used to manufacture such a light detection apparatus, and when in the integrating circuit the capacitance of a capacitor for converting a current into a voltage is changed, the dynamic range for the detection of the intensity of the incident light can be increased.
Such a light detection apparatus is disclosed, for example, in reference document “A 32-Channel Charge Readout IC for Programmable, Nonlinear Quantization of Multichannel Detector Data,” S. L. Garverick, et al., IEEE Journal of Solid-State Circuits, Vol. 30, No. 5, pp. 533-541 (1995).
In the same referenced document, the light detection apparatus having an integrating circuit in which an integrating capacitor unit having a variable capacitance is provided between the input/output terminals of an amplifier is shown. The integrating circuit integrates the charges output by a light detection device in the integrating capacitor unit, and outputs a voltage having a value consonant with the amount of the integrated charges.
For the light detection apparatus in this reference, the capacitance of the integrating capacitor unit is controlled from outside the apparatus to increase the dynamic range for the detection of the intensity of the incident light.
That is, when the capacitance of the integrating capacitor unit is reduced, the detection sensitivity is increased, even when the intensity of the incident light is low. Meanwhile, when the capacitance of the integrating capacitor unit is increased, saturation of an output signal can be avoided, even when the intensity of the incident light is high.
With the light detection apparatus (solid-state image pickup apparatus) described in the above referenced document, even during the daytime in the middle of summer, for example, when conditions are such that the surroundings are brightly lighted, an object can be imaged without saturation of an output signal occurring. Further, when conditions are such that the surroundings are very dark, such as at night, it is possible to image an object with high sensitivity.